Plants use energy from sunlight to power the synthesis of glucose, which they can use immediately or store as starch, a polymer of glucose. When plants need the energy stored in starch (for example, when a seed germinates), plant enzymes hydrolyze the starch into sugars. Animals use starch for energy, too, but instead of making it, they get it by eating plants. Two enzymes that hydrolyze starch are amylase and amyloglucosidase. The introduction to the student activity includes a description of the brewing process, which involves amylase action. The student activity also notes that humans have a salivary amylase and a pancreatic amylase, which are encoded by different, though similar, genes. In this activity, students are asked to test dog saliva for amylase. In the last chapter of this section, students learn how to use the online bioinformatics resources, which include programs for searching the recent biomedical literature.

(A) The sugar glucose. The corners of the hexagon are carbon atoms. (B) Starch. Starch is a polymer of glucose. In this representation, only the hexagons and the linking oxygen atoms are shown. (C) Hydrolysis of starch. When starch is hydrolyzed, a water molecule splits the bond linking two glucose residues. Complete hydrolysis of starch yields glucose.

10.1128/9781555816100/fig31-1_thmb.gif

10.1128/9781555816100/fig31-1.gif

Figure 31.1

(A) The sugar glucose. The corners of the hexagon are carbon atoms. (B) Starch. Starch is a polymer of glucose. In this representation, only the hexagons and the linking oxygen atoms are shown. (C) Hydrolysis of starch. When starch is hydrolyzed, a water molecule splits the bond linking two glucose residues. Complete hydrolysis of starch yields glucose.

The starch-iodine complex. A stylized sketch of the helical starch molecule is shown on the left. On the right, two molecules of iodine (I2, represented by the dumbbell shapes) nestle inside the helix. Six turns of the helix are required to produce a blue color.

10.1128/9781555816100/fig31-2_thmb.gif

10.1128/9781555816100/fig31-2.gif

Figure 31.2

The starch-iodine complex. A stylized sketch of the helical starch molecule is shown on the left. On the right, two molecules of iodine (I2, represented by the dumbbell shapes) nestle inside the helix. Six turns of the helix are required to produce a blue color.